1. Field of the Invention
The present invention relates to an improved photosensitive material for use in electrophotography which is prepared by forming a barrier layer and a photosensitive layer, in that order, on a conductive support.
2. Description of the Prior Art
Generally speaking, in the case of photosensitive materials prepared by dispersing pigments in a resinous binder, there is observed, more or less, a tendency that it becomes hard to charge them with electricity or to increase their potential holdability in the dark (dark decay) gradually as a result of repetition of the electrification-exposure operation. Such changes in characteristics of photosensitive materials would have a very bad effect at the time of taking numerous copies in a PPC-type copying system. Therefore, as an attempt to eliminate the foregoing bad effect, the provision of a barrier layer containing some organic substance and/or inorganic substance interposed between a conductive support and a photosensitive layer has been tried.
The primary object of this barrier layer is to prevent infiltration of unnecessary electric charge through the conductive support and to maintain an appropriate charge acceptability. Another object of this barrier layer is to impart an adhesive property to the photosensitive layer in relation to the support or flexibility to the photosensitive material as a whole. Accordingly, the material constituting the barrier layer is required to combine functions sufficient for realizing both objects and, at the same time, it should not degenerate other characteristics (such as photosensitivity, residual potential, etc.). And, in order to form a photosensitive layer on this barrier layer, the method of coating with a photosensitive layer-forming liquid is usually employed. On this occasion, however, the barrier layer is apt to be dissolved by the solvent contained in said photosensitive layer-forming liquid and the barrier layer tends to commingle with the photosensitive layer. Since it is conceivable that this phenomenon may cause infiltration of unnecessary electric charge into the barrier layer and decrease the electric charge acceptability thereof, thereby rendering it impossible to achieve the primary object of the barrier layer, it becomes necessary to make the coating film of the barrier layer thicker. However, thickening of the coating film of the barrier layer will result a decrease in the electric charge acceptability and an increase in the residual potential.